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.\"     from: @(#)fork.2	6.5 (Berkeley) 3/10/91
.\"	$Id: i386_get_ldt.2,v 1.1 1994/01/31 12:05:30 davidg Exp $
.\"
.Dd September 20, 1993
.Dt I386_GET_LDT 2
.Os FreeBSD
.Sh NAME
.Nm i386_get_ldt ,
.Nm i386_set_ldt
.Nd manage i386 per-process Local Descriptor Table entries
.Sh SYNOPSIS
.Fd #include <machine/segments.h>
.Fd #include <machine/sysarch.h>
.Ft int
.Fn i386_get_ldt "int start_sel" "union descriptor *descs" "int num_sels"
.Ft int
.Fn i386_set_ldt "int start_sel" "union descriptor *descs" "int num_sels"
.Sh DESCRIPTION
.Fn i386_get_ldt
will return the list of i386 descriptors that the process has in its
LDT.
.Fn i386_set_ldt
will set a list of i386 descriptors for the current process in its
LDT.
Both routines accept a starting selector number
.Fa start_sel
, an array of memory that
will contain the descriptors to be set or returned 
.Fa descs
, and the number of entries to set or return
.Fa num_sels .
.Pp
The argument
.Fa descs
can be either segment_descriptor or gate_descriptor and are defined in
.Fd <i386/segments.h> .
These structures are defined by the architecure
as disjoint bit-fields, so care must be taken in constructing them.
.Sh RETURN VALUES
Upon successful completion,
.Fn i386_get_ldt
returns the number of descriptors currently in the LDT.
.Fn i386_set_ldt
returns the first selector set.
Otherwise, a value of -1 is returned and the global
variable
.Va errno
is set to indicate the error.
.Sh ERRORS
.Fn i386_get_ldt
and
.Fn i386_set_ldt
will fail if:
.Bl -tag -width [EINVAL]
.It Bq Er EINVAL
An inappropriate parameter was used for
.Fa start_sel
or
.Fa num_sels .
.It Bq Er EACESS
The caller attempted to use a descriptor that would
circumvent protection or cause a failure.
.El
.Sh REFERENCES
i386 Microprocessor Programmer's Reference Manual, Intel
.Sh WARNING
You can really hose your process using this.
